This invention relates generally to positioning systems, and more particularly to systems for holding a load, such as a patient, in position or for moving the load in a guided manner.
Many industries use positioning systems to raise and hold large loads for a predetermined period of time or guide the large loads along a path. For instance, in the medical industry patients must be raised and held in a predetermined position so that a surgeon may operate on the patient or so that a technician may acquire an image of the patient. When taking medical images of a patient, such as by radiographic or fluoroscopic imaging, the patient must remain in a predetermined position or moved along a predetermined path while the image or images are being acquired. The positioning system may use, for example, a table that starts from a lowered position where the patient can initially sit or lie down on the table and then moves to a raised position within the imaging field.
However, conventional positioning systems have limited movement capabilities and/or load capacities. For example, some known positioning systems include scissor mechanisms that lift the table from the floor to the raised position. The positioning systems that use scissor mechanisms are generally limited to vertical movement and allow little, if any rotational or lateral movement when the scissor mechanisms are fully extended. In addition, the scissor mechanisms are generally located along sides of the table, which may limit access to the table or movement of an imaging device around the table. Also, the scissor mechanisms typically provide a carving mechanical advantage that may require a more complex method of providing power to the scissor mechanism in order for the movement to be constant. Other known positioning systems use multi-stage lifts/pedestals or poles to move the table. However, like the positioning systems that use scissor mechanisms, the multi-stage systems have limited movement capabilities and load capacities.
Thus, there is a need for positioning systems that allow for greater movement capabilities and load capacities than known positioning systems. Also, there is a need for positioning systems that use a reduced amount of space under the table or support. Further, there is a need for positioning systems that provide a substantially constant mechanical advantage.